1. Field of the Invention
This invention relates to a method for the production of cyclohexanecarboguanamine. More particularly, it relates to a method for the production of cyclohexanecarboguanamine represented by the following formula I, which is useful as a resin material for molding materials, laminate sheet materials, and vehicles in coating materials and as a starting material for resin modifiers and medicines: ##STR1##
2. Description of the Prior Art
A method for the synthesis of guanamine compounds by the thermal reaction of fatty acid nitriles with dicyandiamide has been widely known to the art [Smolin and Rapoport: "The Chemistry of Heterocyclic Compounds (s-Triazine and Derivatives)," 1959, page 229, Interscience Publishers Inc. and Japanese Patent Publication SHO 40(1965)-2,353 and SHO 40(1965)-22,190, etc.].
A method for the synthesis of cyclohexanecarboguanamine is disclosed in U.S. Pat. No. 3,379,661. In Example 1 cited in the specification of this U.S. patent, it is stated that cyclohexanecarboguanamine was obtained by placing cyanocylohexane and dicyandiamide in ethylene glycol monomethyl ether solvent and boiling the solvent in the presence of a potassium hydroxide catalyst thereby effecting a reaction. The method disclosed in the U.S. patent is based on the well-known method for the production of guanamine compounds.
We have found that the cyclohexanecarboguanamine obtained by the conventional method available for the production of guanamines is colored and must be purified into a white product of high quality to be used satisfactorily as a material for various resin products, as a resin modifier, or as a starting material for medicines. A method for the purification of guanamine compounds is disclosed in Japanese Patent Publication SHO 38(1963)-8,328 and SHO 38(1963)-8,329, for example. By this method, white guanamines are obtained by purifying guanamine compounds by means of recrystallization or sublimation. This method, therefore, involves many steps of operation and proves to be a process of poor economy.
In U.S. Pat. No. 3,379,661, there is no mention of the yield of production. We tried to synthesize cyclohexanecarboguanamine in accordance with the method disclosed in the U.S. patent and obtained the compound only in low yield (as demonstrated in Control 2 cited thereinafter).
As a method for the production of cyclohexanecarboguanamine, the present invention contemplates a method of sequentially adding dicyandiamide to a solvent containing cyanocyclohexane. There have existed similar methods which synthesize guanamine compounds from fatty acid nitriles by sequential addition of dicyandiamide in French Patent No. 1,390,116 and U.S. Pat. No. 2,606,904, for example. According to the French Patent, a sulfoxide such as dimethyl sulfoxide is used as a solvent and dicyandiamide is added over a period of at least one hour to a fatty acid nitriles dissolved in advance in the solvent. The French patent mentioned above does not teach any method using cyanocyclohexane as a fatty acid nitrile.
We followed a specific method disclosed in the French patent to try synthesis of cyclohexanecarboguanamine using cyanocyclohexane as a cyan compound and obtained the compound only in low yield. All these results imply that the method of the French Patent resorting to sequential addition and using sulfoxide as a solvent is not always suitable for the reaction under discussion.
In accordance with the method disclosed in U.S. Pat. No. 2,606,904, it is stated that, in the reaction of dicyandiamide with a higher fatty acid nitrile possessing an alkyl or alkenyl group of not less than 8 carbon atoms, sequential addition of the dicyandiamide results in the production of a corresponding guanamine in a yield in the range of 60 to 70%. This yield of the reaction, however, is not sufficient for the method to be fully feasible from the commercial point of view.
In the conventional method for synthesizing a guanamine compound from a fatty acid nitrile and dicyandiamide, it is normal to use the dicyandiamide in a ratio of not less than one mole per mole of the fatty acid nitrile.
Other methods for the synthesis of cyanocyclohexane, a starting material for the method of the present invention, are disclosed in U.S. Pat. No. 3,379,661, Japanese Patent Publication SHO 50(1975)-1,034, and U.S. Pat. No. 4,673,757. The method of U.S. Pat. No. 3,379,661 comprises hydrogenating cyanocyclohexene under a pressure of 1,000 lb/in.sup.2 (equal to about 70.3 kg/cm.sup.2) in the presence of a palladium catalyst supported on carbon thereby effecting synthesis of cyanocyclohexane. This U.S. patent has absolutely no disclosure about such reaction conditions as reaction temperature and amount of catalyst. The disclosure only goes to the length of suggesting the possibility of the reaction. Absolutely no mention is made of the quality of the produced cyanocylohexane anywhere in the specification thereof. Further, this method has a disadvantage that the reaction pressure is so high as to require use of an expensive apparatus. The method disclosed in Japanese Patent Publication SHO 50(1975)-1,034 comprises subjecting 4-cyanocyclohexene to hydrogenation at a temperature in the range of 100.degree. to 110.degree. C. under a pressure of 80 to 100 atmospheres in the presence of a rhodium trichloride catalyst thereby producing cyanocyclohexane. This method similarly has a disadvantage that the reaction pressure is so high as to require use of an expensive apparatus. It also requires use of an expensive catalyst and does not fit commercialization. The method disclosed in U.S. Pat. No. 4,673,757 comprises hydrogenating cyanocyclohexene at a temperature of 120.degree. C. in the presence of a ruthenium-triphenyl phosphine catalyst thereby producing cyanocyclohexane. This method is similarly unfit for commercialization because it requires use of an expensive catalyst.
An object of this invention is to provide a method for the production of cyclohexanecarboguanamine of high purity.
Another object of this invention is to provide an economically advantageous method for commercial production of uncolored white cyclohexanecarboguanamine of high quality in high yield enough to be used as a starting material for various resin materials, resin modifier, and medicines.
Yet another object of this invention is to provide an economically advantageous method for commercial production of cyanocyclohexane of high quality in high yeild enough to be used as a raw material for the synthesis of the cyclohexanecarboguanamine mentioned above.